Particle collecting device and image forming apparatus

ABSTRACT

A particle collecting device includes: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air. The collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2020-047654 filed Mar. 18, 2020.

BACKGROUND (i) Technical Field

The present disclosure relates to a particle collecting device and animage forming apparatus.

(ii) Related Art

Japanese Unexamined Patent Application Publication No. 2008-8151 (claim1, FIG. 1, and others) describes a honeycomb structure that is a secondhoneycomb structure used in an air discharging system of an internalcombustion engine in which at least one or more first honeycombstructures and at least one or more second honeycomb structures aredisposed. The honeycomb structure has a pressure loss smaller than apressure loss of one of the first honeycomb structures, and includes twoor more electrodes.

Japanese Unexamined Patent Application Publication No. 2012-32663 (claim1, paragraph 0027, FIG. 2, and others) describes an image formingapparatus that fixes a toner image, which has been transferred onto asheet in an image forming unit, by heating and pressing the toner imagein a fixing unit. The image forming apparatus includes a fan fordischarging cooling air, which has been used to cool the fixing unit,from the fixing unit; an air discharging duct for discharging thecooling air, which has been discharged from the fixing unit, to theoutside of the apparatus; and a filter unit disposed in the airdischarging duct. The filter unit includes a filter that is impregnatedwith silicone oil. Japanese Unexamined Patent Application PublicationNo. 2012-32663 also shows examples of the shape of the siliconeimpregnated filter, such as a honeycomb shape.

SUMMARY

Aspects of non-limiting embodiments of the present disclosure relate toa particle collecting device and an image forming apparatus using theparticle collecting device. The particle collecting device is capable ofcollecting and reducing ultra-fine particles having a particle diameterof 100 μm or smaller while suppressing pressure loss, compared with acase where a plate-shaped air-permeable member having a honeycombstructure such that the number of cells per square inch or the openingratio per square inch is in a specific numerical range is not used as acollecting unit.

Aspects of certain non-limiting embodiments of the present disclosureaddress the above advantages and/or other advantages not describedabove. However, aspects of the non-limiting embodiments are not requiredto address the advantages described above, and aspects of thenon-limiting embodiments of the present disclosure may not addressadvantages described above.

According to an aspect of the present disclosure, there is provided aparticle collecting device including: an air pipe having a flow space inwhich air including particles flows; and a collecting unit that isdisposed in such a way as to block the flow space of the air pipe andthat collects the particles included in the air. The collecting unit isa plate-shaped air-permeable member having a honeycomb structure suchthat a number of cells per square inch is 600 or larger and 1400 orsmaller.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present disclosure will be described indetail based on the following figures, wherein:

FIG. 1 is a schematic view illustrating the entirety of an image formingapparatus according to the exemplary embodiment;

FIG. 2 is a schematic view illustrating the configurations of a fixingdevice and a particle collecting device of the image forming apparatusof FIG. 1;

FIG. 3A is a schematic view illustrating the particle collecting deviceof FIG. 2;

FIG. 3B is a schematic view illustrating a plate-shaped air-permeablemember that is a collecting unit of the particle collecting device;

FIG. 4 shows a schematic view and a partial enlarged view of theair-permeable member of FIG. 3B;

FIG. 5 is a schematic view illustrating a test method used in a test T1and the like;

FIG. 6 is a graph illustrating the result of a test of examining therelationship between the particle diameter and the amount of ultra-fineparticles, which indicates the collection efficiency of the particlecollecting device;

FIG. 7 is a graph illustrating the result of a test of examining therelationship among the number of cells of a honeycomb structure of theair-permeable member, the thickness of the air-permeable member, and theultra-fine-particle collection efficiency;

FIG. 8A is a graph illustrating the result of a test T2 of examining therelationship between the number of cells of the honeycomb structure ofthe air-permeable member and the pressure loss;

FIG. 8B is a graph illustrating the result of a test of examining therelationship between the ultra-fine-particle reduction ratio of theair-permeable member and the airflow rate;

FIG. 9 is a graph illustrating the relationship between the number ofcells of the honeycomb structure of the air-permeable member and theopening ratio of the honeycomb structure, for different thicknesses of aboundary portion between the cells; and

FIG. 10 is a graph re-illustrating the result of FIG. 7 by taking theopening ratio along the horizontal axis.

DETAILED DESCRIPTION

Hereafter, an exemplary embodiment of the present disclosure will bedescribed with reference to the drawings.

Exemplary Embodiment

FIGS. 1 and 2 illustrate an image forming apparatus and a particlecollecting device according to an exemplary embodiment of the presentdisclosure. FIG. 1 illustrates the entirety of the image formingapparatus, and FIG. 2 illustrates a part (including a fixing device andthe particle collecting device) of the image forming apparatus.

In FIG. 1 and other figures, arrows X, Y, and Z respectively indicatethe width direction, the height direction, and the depth direction of athree-dimensional space assumed for each of the figures. In each of thefigures, a blank circle at the intersection of the arrow X and the arrowY indicates that the arrow Z extends into the plane of the figure.

Image Forming Apparatus

FIG. 1 illustrates an image forming apparatus 1 that forms an image on asheet 9, which is an example of a recording medium, by using, forexample, an electrophotographic method. The image forming apparatus 1forms an image corresponding to, for example, image information that isinput from an external device such as an information terminal. Here, theterm “image information” refers to information related to an image to beformed, such as a character, a figure, a photograph, a pattern, or thelike.

Referring to FIG. 1, the image forming apparatus 1 includes: a housing10, which is an example of an apparatus body; and an image formingdevice 2, a sheet feeding device 4, a fixing device 5, a particlecollecting device 6, and the like, which are disposed in the housing 10.

The housing 10 is made from components, such as support members andexterior members, so as to have desirable shape and structure. In FIG.1, a chain line with an arrow indicates a transport path along which thesheet 9 is transported in the housing 10.

The image forming device 2 forms a toner image, which is composed oftoner as a developer, based on image information and transfers the tonerimage to the sheet 9. The image forming device 2 includes: anphotoconductor drum 21, which is an example of an image carrier andwhich rotates in the direction indicated by an arrow A; and a chargingdevice 22, an exposure device 23, a developing device 24, a transferdevice 25, a cleaning device 26, and the like, which are disposed aroundthe photoconductor drum 21.

The charging device 22 charges the outer peripheral surface (imageforming surface) of the photoconductor drum 21 to a desirable surfacepotential. The charging device 22 includes, for example, a chargingmember such as a roller that is in contact with an image forming regionof the outer peripheral surface of the photoconductor drum 21 and towhich a charging electric current is supplied. The exposure device 23forms an electrostatic latent image on the outer peripheral surface ofthe photoconductor drum 21, which has been charged, by exposing theouter peripheral surface to light based on image information. Theexposure device 23 is operated based on an image signal that isgenerated by an image processor (not shown) by performing a desirableimage processing operation on image information that is input from theoutside.

The developing device 24 develops the electrostatic latent image, whichhas been formed on the outer peripheral surface of the photoconductordrum 21, into a monochrome toner image by using developer (toner) havinga predetermined color (for example, black). The transfer device 25electrostatically transfers the toner image, which has been formed onthe outer peripheral surface of the photoconductor drum 21, to the sheet9. The transfer device 25 includes a transfer member such as a transferroller that is in contact with the outer peripheral surface of thephotoconductor drum 21 and to which a transfer electric current issupplied. The cleaning device 26 cleans the outer peripheral surface ofthe photoconductor drum 21 by scraping off waste substances that adhereto the outer peripheral surface of the photoconductor drum 21, such asresidual toner, paper dust, and the like.

In the image forming device 2, a position at which the photoconductordrum 21 and the transfer device 25 face each other is a transferposition TP where transfer of a toner image is performed.

The sheet feeding device 4 stores sheets 9, which are to be supplied tothe transfer position TP in the image forming device 2, and feeds thesheets 9. The sheet feeding device 4 includes a container 41 that storesthe sheets 9, a feeding device 43 that feeds the sheets 9, and the like.

The container 41 includes a stacking plate (not shown) on which pluralsheets 9 are stacked in a desirable orientation. The container 41 isattached to the housing 10 in such a way that a user can perform, forexample, an operation of supplying sheets 9 by pulling the container outof the housing 10. The feeding device 43 feeds the sheets 9, which arestacked on the staking plate of the container 41, one by one by using afeeding mechanism having plural rollers or the like.

The sheet 9 may be any recording medium, such as plain paper, coatedpaper, or cardboard, that can be transported in the housing 10 and towhich a toner image can be transferred and fixed. The material, theshape, and the like of the sheet 9 are not particularly limited.

The fixing device 5 fixes a toner image, which has been transferred atthe transfer position TP in the image forming device 2, to the sheet 9.The fixing device 5 includes: a housing 50 having an input opening 50 aand an output opening 50 b for the sheet 9; and a heating rotationalbody 51, a pressing rotational body 52, and the like, which are disposedin the housing 50.

The heating rotational body 51 may be a roller, a belt-pad, or the likethat rotates in the direction indicated by an arrow. The heatingrotational body 51 is heated by a heater (not shown) so that thetemperature of the outer surface thereof is maintained at a desirabletemperature. The pressing rotational body 52 may be a roller, abelt-pad, or the like that is rotated by or rotates the heatingrotational body 51 by being pressed against the heating rotational body51 with a desirable pressure. The pressing rotational body 52 may beheated by a heater.

In the fixing device 5, a portion at which the heating rotational body51 and the pressing rotational body 52 are in contact with each other isa fixing-operation portion (nip) FN where operations such as a heatingoperation and a fixing operation for fixing an unfixed toner image tothe sheet 9 are performed.

In FIG. 1, the chain line represents a sheet transport path Rt1 alongwhich the sheet 9 is transported from the sheet feeding device 4 andsupplied to the transfer position TP. In the sheet transport path Rt1,plural transport rollers 44 a and 44 b that nip the sheet 9 therebetweenand transport the sheet 9, guide members (not shown) that provide atransport space for the sheet 9 and guide transporting of the sheet 9,and the like are disposed.

The image forming apparatus 1 performs an image forming operation, forexample, as follows.

When a controller (not shown) of the image forming apparatus 1 receivesan instruction for performing an image forming operation, the imageforming device 2 performs a charging operation, an exposure operation, adeveloping operation, and a transfer operation, while the sheet feedingdevice 4 performs a sheet feeding operation of feeding the sheet 9 tothe transfer position TP. Thus, a toner image is formed on thephotoconductor drum 21, and the toner image is transferred from thesheet feeding device 4 to the sheet 9 supplied to the transfer positionTP.

Next, the fixing device 5 of the image forming apparatus 1 performs afixing operation in which the sheet 9, on which the toner image has beentransferred, is guided into and passes through the nip FN. Thus, theunfixed toner image is fixed to the sheet 9. The sheet 9, on which thetoner image has been fixed, is discharged by, for example, an outputroller 45 to a container (not shown) disposed outside of the housing 10.

Thus, the image forming apparatus 1 finishes the image forming operationof forming an image on one side of the sheet 9.

Particle Collecting Device

The particle collecting device 6 collects particles generated in thefixing device 5 and the surrounding components. Referring to FIGS. 1 to3B and other figures, the particle collecting device 6 includes an airpipe 61, an airflow generating unit 62, a collecting unit 63, and thelike.

The particle collecting device 6 collects ultra-fine particles (UFPs)having a particle diameter of 100 nm (0.1 μm) or smaller.

The particle collecting device 6 collects, for example, ultra-fineparticles that are included in particles (dust particles) that aregenerated when wax and other materials of toner are vaporized by heatduring a fixing process (fixing operation) and then cooled.

The air pipe 61 has a flow space 61 a in which air including particlesflows.

The air pipe 61 in the exemplary embodiment is a rectangular pipe inwhich the flow space 61 a has a substantially rectangularcross-sectional shape. Referring to FIGS. 2 and 3A, one end portion 61 bof the air pipe 61 is connected to a suction duct 56 of an airdischarging mechanism 55, which is an example of an air dischargingunit, disposed on a side portion of the housing 50 of the fixing device5. The other end portion 61 c of the air pipe 61 is connected to anair-discharge opening 12 of the air discharging mechanism 55, which isformed in a back portion 10 e of the housing 10. The suction duct 56sucks air that is present in the housing 50 and the surrounding areathrough a suction opening 56 a, which is located above the input opening50 a and the output opening 50 b for the sheet 9, of the housing 50 ofthe fixing device 5. In FIG. 2, the numeral 10 d represents an upperportion of the housing 10.

The airflow generating unit 62 generates airflow for causing air to flowin the flow space 61 a of the air pipe 61 in a direction C in which theair is to be moved.

In the exemplary embodiment, an axial fan is used as the airflowgenerating unit 62. Referring to FIG. 3A, the axial fan includes, forexample, a frame 621 in which a through-portion 621 a having a circularcross-sectional shape is formed, a shaft 622 that is rotatably supportedin the through-portion 621 a of the frame 621 and in which a drivingmotor (not shown) is disposed, and plural blades 623 that are disposedso as to stand around the shaft 622.

The intensity (the airflow rate or the airflow speed) of airflowgenerated by the airflow generating unit 62 may be appropriatelydetermined in view of, for example: prevention of secondary problems,such as increase of temperature and occurrence of condensation insidethe housing 10 of the image forming apparatus 1 (in the present example,particularly the inside of the housing 50 of the fixing device 5) andincrease of operation noise; and achievement of high particle-collectingperformance of the collecting unit 63. As can be seen from the testresults described below, the UFP reduction ratio (collection efficiency)tends to increase as the airflow rate increases. Therefore, for example,the airflow rate on a side of the collecting unit 63 into which airflows may be 0.2 m³/min or higher.

The collecting unit 63 is disposed across the flow space 61 a in amiddle part of the air pipe 61 and collects particles included in airthat flows in the flow space 61 a.

Referring to FIG. 3B and other figures, the collecting unit 63 in theexemplary embodiment includes a plate-shaped air-permeable member 66having a honeycomb structure such that the number of cells 65 per squareinch is 600 or larger and 1400 or smaller. Referring to the partiallyenlarged view in FIG. 4, the plate-shaped air-permeable member 66 is,for example, a metal filter having a honeycomb structure such that thecells 65, each having a substantially hexagonal cross-sectional shape,are tightly arranged.

Here, each of the cells 65 is a minimum unit of the repeating pattern ofthe honeycomb structure, and has a hollow tubular structure extendingthrough the honeycomb structure while maintaining a uniformcross-sectional shape. The number of the cells 65 per square inch iscounted, for example, by performing image processing analysis or byusing a tool such as a magnifying glass.

Referring to FIGS. 3A and 3B, the collecting unit 63, which includes theplate-shaped air-permeable member 66 having the honeycomb structure, is,for example, fixed to the inside of the flow space 61 a of the air pipe61 in a state of being attached to and supported by a frame 64 having anair-permeable region.

The plate-shaped air-permeable member 66, which is a metal filter, ismanufactured by using a metal material such as aluminum. It is notnecessary to apply a material having a function of improving theultra-fine-particle collection performance or the like to the surface ofthe collecting unit 63, which is a metal filter having the honeycombstructure, and the metal surface may be exposed as it is.

If the number of the cells 65 is smaller than 600, the surface area issmall and it is difficult to obtain sufficient ultra-fine-particlecollection performance. If the number of the cells 65 is larger than1400, it is difficult to suppress pressure loss and to manufacture(process) a plate-shaped air-permeable member having a honeycombstructure with such a number of cells.

In view of suppression of pressure loss and achievement of sufficientlyhigh collection efficiency, the number of the cells 65 may be 900 orlarger and 1000 or smaller.

The thickness D of the collecting unit 63, which includes theplate-shaped air-permeable member 66 having the honeycomb structure, mayhave any appropriate value. However, the thickness D may be 3 mm orlarger and 9 mm or smaller, and further, may be 5 mm or larger and 7 mmor smaller.

Here, the thickness D is the dimension of the collecting unit 63 in thedirection in which the cells 65 extend through the collecting unit 63 orthe direction in which air passes through the collecting unit 63. If thethickness D is smaller than 3 mm, the surface area of each of the cells65 in the direction in which air passes is small, and it is difficult toobtain sufficiently high ultra-fine-particle collection performance. Ifthickness D is larger than 9 mm, it is difficult to suppress pressureloss.

Referring to the enlarged view of FIG. 4, in the collecting unit 63, thethickness t of a boundary portion 67 between the cells 65 of thehoneycomb structure is 0.015 mm or larger and 0.02 mm or smaller.

If the thickness t of the boundary portion 67 is smaller than 0.015 mm,it is difficult to manufacture the plate-shaped air-permeable member ofthe collecting unit 63, and it is difficult to maintain the shape of thehoneycomb structure due to insufficient strength of the plate-shapedair-permeable member. If the thickness t of the boundary portion 67 islarger than 0.02 mm, it is difficult to form a honeycomb structure suchthat the number of the cells 65 is in the aforementioned range.

Referring to FIGS. 2 and 3A, in the particle collecting device 6, thecollecting unit 63 is disposed at a position in the air pipe 61downstream of the airflow generating unit 62 in the direction C in whichair is moved in the flow space 61 a of the air pipe 61. In view ofsuppressing gap leakage between the frame 64 and the air pipe 61, thecollecting unit 63 may be disposed at a position in the air pipe 61upstream of the airflow generating unit 62 in the direction C in whichair flows in the air pipe 61.

The particle collecting device 6 operates, for example, at least whenthe fixing device 5 is operating and for a predetermined period afterthe fixing device 5 has stopped operating.

That is, referring to FIG. 3A, when the particle collecting device 6operates, the airflow generating unit 62 is activated, and airflow inthe direction of an arrow C is generated in the flow space 61 a of theair pipe 61.

Thus, air including particles generated in a fixing operation of thefixing device 5 flows into the flow space 61 a of the air pipe 61 viathe suction duct 56. Air Ea including particles, which has flowed intothe flow space 61 a, passes through the axial fan of the airflowgenerating unit 62 and is moved to the front side of the collecting unit63 as unfiltered air Eb.

Referring to FIG. 3A, the unfiltered air Eb including particles, whichhas been moved to the front side of the collecting unit 63, collideswith the plate-shaped air-permeable member 66, having the honeycombstructure, of the collecting unit 63 and moves so as to pass through thecells 65 of the honeycomb structure.

That is, the unfiltered air Eb passes through the cells 65 of theplate-shaped air-permeable member 66 while colliding with theair-permeable member 66 (metal filter) having the honeycomb structuresuch that the number of the cells 65 per square inch is 600 or largerand 1400 or smaller.

Thus, at least some of ultra-fine particles that are included in theunfiltered air Eb and that have a particle diameter of 100 nm or smalleradhere to the cells 65 of the honeycomb structure of the plate-shapedair-permeable member 66 and are collected. As a result, compared withthe unfiltered air Eb, ultra-fine particles included in filtered air Ecthat has passed through the collecting unit 63 are reduced.

Lastly, the filtered air Ec is discharged to the outside from theair-discharge opening 12 of the housing 10 of the image formingapparatus 1.

Tests Related to Collection Efficiency

Next, a test T1 performed to examine the collection efficiency of theparticle collecting device 6 will be described.

The test T1 related to the collection efficiency is performed based onthe test standards (RAL-UZ205) of Blue Angel mark, which is the Germanecolabel.

Referring to FIG. 5, the test T1 is performed as follows: the imageforming apparatus 1 to be measured is placed on a placement base 120disposed in a space 110 of a test chamber 100, which is ahermetically-closed test environment chamber, so as to be inequilibrium; the image forming apparatus 1 is activated, and apredetermined image forming operation is performed for one minute; andthe amount of ultra-fine particles (UFP) included in air in the indoorspace and the like during the image forming operation and in apredetermined period after stopping the operation is measured by using ameasuring device 150 (Condensation Particle Counter CPC Model 3775, madeby TSI Incorporated). In the test T1, the test chamber 100 is set to bein a predetermined indoor environment (temperature: 23° C., humidity:50% RH).

The test chamber 100 has an indoor space having a volume of, forexample, 5.1 m³. Clean air 132 is supplied to the indoor space from anair-supply opening 103, and indoor air 133 is discharged from anair-discharge opening 104. The indoor air 133 discharged from the testchamber 100 is moved to the measuring device 150 connected to the testchamber 100.

The image forming apparatus 1 to be measured is combined with theparticle collecting device 6 including the collecting unit 63 having theplate-shaped air-permeable member 66 configured as described below. As acomparative example, an image forming apparatus combined with theparticle collecting device 6 to which the collecting unit 63 is notattached is prepared.

As the plate-shaped air-permeable member 66, an aluminum filter having athickness D of 6 mm and having a honeycomb structure such that thenumber of the cells 65, each having a substantially hexagonalcross-sectional shape, is approximately 950 is used. In the particlecollecting device 6, the total area of a portion of the air-permeablemember 66 of the collecting unit 63 that comes into contact with air is14400 mm². In the particle collecting device 6, the axial fan, which isthe airflow generating unit 62, is rotated so that the airflow rate on aside (upstream side) of the air-permeable member 66 into which air flowsis 0.33 m³/min. The particle collecting device 6 is operated for aperiod from the start to the end of the image forming operation in thetest.

An image formed in the image forming operation is a chart having animage area ratio of 5%, which is designated by Blue Angel (BA). As thefixing device 5, a device that performs a fixing operation at afixing-heating temperature in the range of 150 to 180° C. is used. Asthe toner, a toner composed of resin, pigment, wax particles, and thelike is used.

In the test T1, the relationship between the particle diameter and thenumber of ultra-fine particles (number of UFPs) is examined. FIG. 6shows the result.

In the test T1, the image forming apparatus according to the comparativeexample (including the particle collecting device 6 to which thecollecting unit 63 is not attached) is also tested under the sameconditions.

From the result shown in FIG. 6, it can be seen that, in a case wherethe image forming apparatus including the particle collecting device 6to which the plate-shaped air-permeable member 66 having the honeycombstructure is attached (with a filter) is used, the amount of UFPs havinga particle diameter of 100 nm or smaller is reduced, compared with acase where the image forming apparatus according to the comparativeexample (without a filter) is used.

Next, regarding the air-permeable member 66 of the collecting unit 63that can reduce the amount of UFPs, the test T1 is performed to examinethe relationship among the number of the cells 65 of the air-permeablemember 66, the thickness D of the air-permeable member 66, and the UFPcollection efficiency. FIG. 7 shows the result of the test T1.

The test T1 is performed as follow: the plate-shaped air-permeablemembers 66, which are aluminum filters having different numbers of cells65 and different thicknesses D, are prepared; and the UFP collectionefficiency when the air-permeable members 66 are replaced with eachother and each attached to the particle collecting device 6 is measured.

Nine air-permeable members 66 having the following combinations areprepared: the numbers of cells 65 was 600, 950, and 1400; and thethicknesses D of the air-permeable members 66 was 3 mm, 6 mm, and 9 mmas shown in FIG. 7.

The collection efficiency is the difference in percent between the UFPamount when each of the air-permeable members 66 is present and the UFPamount when the air-permeable member 66 is not present, and alsocorresponds to the UFP reduction ratio.

From the result shown in FIG. 7, it can be seen that the UFP collectionefficiency gradually increases as the number of the cells 65 per squareinch increases. From the result, it can be also seen that, for the samenumber of cells, the UFP collection efficiency gradually increases asthe thickness D of the air-permeable member 66 increases.

Therefore, it can be said that, in the air-permeable member 66, having ahoneycomb structure, of the collecting unit 63, there is a substantiallyproportional correlation between the number of the cells 65 and thethickness D the air-permeable member 66 and the UFP collectionefficiency.

From the result, it can be said that the air-permeable member 66 havinga honeycomb structure has an effect of collecting and reducing UFPs,provided that the number of the cells 65 is 600 or larger and 1400 orsmaller and the thickness D of the air-permeable member 66 is 3 mm orlarger and 9 mm or smaller.

Next, a test T2 is performed to examine the relationship between thenumber of the cells 65 of the air-permeable member 66, which is thecollecting unit 63 of the particle collecting device 6, and the pressureloss.

FIG. 8A shows the result of the test T2.

In the test T2, the air-permeable members 66 such that the numbers ofcells 65 are 600, 950, and 1400 are prepared. The air-permeable members66 are the same as the aluminum filters used in the test T1, and eachhas a thickness D of 6 mm.

In the test T2, the pressure loss is measured as follows: in theparticle collecting device 6, the air-permeable members 66 such that thenumbers of cells were the aforementioned values are replaced with eachother and each set in the air pipe 61; airflow of a predetermined flowrate (0.33 m³/min) is generated by the airflow generating unit 62; andthe difference between the air pressure (Pa) at a position upstream ofthe air-permeable member 66 and the air pressure (Pa) at a positiondownstream of the air-permeable member 66 is obtained as the pressureloss (Pa). The air pressure is measured by using a differential pressuregauge (Model 5122, made by Testo SE & Co.).

From the result shown in FIG. 8A, it can be seen that the pressure lossof the air-permeable members 66 having the aforementioned numbers ofcells is in the range of approximately 2 to 8.5 Pa. It can be said that,when the pressure loss is in such a range, the pressure loss issufficiently suppressed. From the result, it can be also seen that, inthe air-permeable member 66, the pressure loss gradually increases asthe number of cells increases.

Accordingly, when the results of the test T1 are also taken intoaccount, the particle collecting device 6 can collect UFPs whilesuppressing pressure loss.

The pressure loss of the particle collecting device 6 may be 6 Pa orsmaller, because, in this case, a load applied the axial fan of theairflow generating unit 62 is reduced and the power consumption tends todecrease, and the noise of the axial fan is further reduced.

Next, the test T1 is performed to examine the relationship between theUFP reduction ratio and the airflow rate of the air-permeable member 66of the collecting unit 63.

FIG. 8B shows the result of the test.

In this test, as the air-permeable member 66, an aluminum filter havinga honeycomb structure such that the number of cells is 950 is used. Thethickness D of the air-permeable member 66 is 6 mm.

In this test, by adjusting the rotation speed of the axial fan of theairflow generating unit 62, the airflow rate on the side of thecollecting unit 63 into which air flows is set to 0.15, 0.33, and 0.53(m³/min). The UFP reduction ratio is obtained in the same way as thecollection efficiency is obtained in the test T1.

From the result shown in FIG. 8B, it can be seen that, with theair-permeable member 66 having the aforementioned number of cells, theUFP reduction ratio tends to increase as the airflow rate increases (asthe airflow rate increases to 0.2 m³/min or higher).

Because the UFP reduction ratio (collection efficiency) is desirably 30%or higher, in view of this, the airflow rate may be set to approximately0.3 m³/min or higher. The upper limit of the airflow rate may be set,for example, in view of reduction of operation noise such as noise ofthe airflow generating unit 62 and the like.

Because an aluminum filter is used as the air-permeable member 66 of thecollecting unit 63 in the particle collecting device 6, theair-permeable member 66 is resistant to corrosion and can be used stablyfor a long time.

In the particle collecting device 6, the plate-shaped air-permeablemember 66 of the collecting unit 63 has a honeycomb structure such thatthe number of the cells 65 per square inch is 600 or larger and 1400 orsmaller and the thickness t of the boundary portion 67 between the cells65 is 0.015 mm or larger and 0.02 mm or smaller. Regarding the honeycombstructure, FIG. 9 illustrates the relationship between the number ofcells per square inch and the opening ratio per square inch.

From the result shown in FIG. 9, regarding the honeycomb structure ofthe air-permeable member 66 described above, it can be paraphrased thatthe honeycomb structure has an opening ratio per square inch in therange of the minimum 94.2% to the maximum 97.1%.

Thus, in the particle collecting device 6, the plate-shapedair-permeable member 66 of the collecting unit 63 may have a honeycombstructure such that the opening ratio per square inch is 94.2% or higherand 97.1% or lower. The opening ratio can be measured by using, forexample, a method that is the same as the aforementioned method ofcounting the number of the cells 65 per square inch.

FIG. 10 is a graph re-illustrating the result shown in FIG. 7, whichrepresents the relationship among the number of the cells 65 of theair-permeable member 66, the thickness D of the air-permeable member 66,and the UFP collection efficiency, by taking the opening ratio, insteadof the number of cells, along the horizontal axis.

From the result shown in FIG. 10, it can be seen that the UFP collectionefficiency gradually increases as the opening ratio per square inch ofthe honeycomb structure decreases. It can be also seen from this resultthat, for the same opening ratio, the UFP collection efficiency tends togradually increase as the thickness D of the air-permeable member 66increases.

Therefore, it can be seen that, with the air-permeable member 66, havinga honeycomb structure, of the collecting unit 63, there is asubstantially proportional correlation between the thickness D of theair-permeable member 66 and the UFP collection efficiency, while it canbe also said that there is a substantially inversely-proportionalcorrelation between the opening ratio per square inch and the UFPcollection efficiency.

Modifications

The present disclosure is not limited to the contents described asexamples in the exemplary embodiment and may be modified in various wayswithin the spirit and scope of the present disclosure described in theclaims. For example, the present disclosure includes the followingmodifications.

In the exemplary embodiment, an aluminum filter is descried as anexample of the plate-shaped air-permeable member 66 of the collectingunit 63. However, as long as the air-permeable member 66 can have adesirable honeycomb structure, an air-permeable member made of a metalother than aluminum or a material other than metal may be used.

In the exemplary embodiment, the particle collecting device 6 includesthe airflow generating unit 62. However, the particle collecting device6 need not include the airflow generating unit 62 if the particlecollecting device 6 is used in combination with an air discharging unitthat generates airflow by using an air-discharge fan or the like. Ablower other than an axial fan may be used as the airflow generatingunit 62.

In the exemplary embodiment, the particle collecting device 6 is used tocollect particles, including ultra-fine particles, generated in thefixing device 5 of the image forming apparatus 1. However, the particlecollecting device 6, which is a device that collects ultra-fineparticles, may be used in combination with an air discharging unit thatsucks and discharges air including ultra-fine particles generated by adevice other than the fixing device 5 of the image forming apparatus 1.

A particle collecting device according to the present disclosure can beused in an apparatus other than an image forming apparatus for whichultra-fine particles need to be collected.

An image forming apparatus in which the particle collecting device 6 isused is not limited to the image forming apparatus 1 described as anexample in the exemplary embodiment, and may be another type of imageforming apparatus using an electrophotographic method (including amulticolor image forming method). Further alternatively, an imageforming apparatus in which the particle collecting device 6 is used maybe an image forming apparatus using an image forming method other thanan electrophotographic method (such as a liquid jet method, a printingmethod, or the like).

The foregoing description of the exemplary embodiment of the presentdisclosure has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit thedisclosure to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and its practical applications, therebyenabling others skilled in the art to understand the disclosure forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of thedisclosure be defined by the following claims and their equivalents.

1. A particle collecting device comprising: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller, wherein a thickness of the air-permeable member is 9 mm or smaller.
 2. A particle collecting device comprising: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that an opening ratio per square inch is 94.2% or higher and 97.1% or lower.
 3. The particle collecting device according to claim 1, wherein a thickness of the air-permeable member is 3 mm or larger.
 4. The particle collecting device according to claim 2, wherein a thickness of the air-permeable member is 3 mm or larger and 9 mm or smaller.
 5. The particle collecting device according to claim 1, wherein a thickness of a boundary portion between the cells of the honeycomb structure is 0.015 mm or larger and 0.02 mm or smaller.
 6. The particle collecting device according to claim 2, wherein a thickness of a boundary portion between the cells of the honeycomb structure is 0.015 mm or larger and 0.02 mm or smaller.
 7. (canceled)
 8. (canceled)
 9. The particle collecting device according to claim 1, wherein the air-permeable member is made of aluminum.
 10. The particle collecting device according to claim 2, wherein the air-permeable member is made of aluminum.
 11. (canceled)
 12. (canceled)
 13. The particle collecting device according to claim 5, wherein the air-permeable member is made of aluminum.
 14. The particle collecting device according to claim 6, wherein the air-permeable member is made of aluminum.
 15. (canceled)
 16. (canceled)
 17. The particle collecting device according to claim 1, comprising: an airflow generating unit that generates airflow that causes the air to flow in the flow space of the air pipe in a direction in which the air is to be moved, wherein the airflow generating unit comprises a fan, wherein the airflow generating unit operates so that an airflow rate on a side of the air-permeable member into which the air flows is 0.2 m³/min or higher.
 18. The particle collecting device according to claim 2, comprising: an airflow generating unit that generates airflow that causes the air to flow in the flow space of the air pipe in a direction in which the air is to be moved, wherein the airflow generating unit comprises a fan, wherein the airflow generating unit operates so that an airflow rate on a side of the air-permeable member into which the air flows is 0.2 m³/min or higher.
 19. The particle collecting device according to claim 3, comprising: an airflow generating unit that generates airflow that causes the air to flow in the flow space of the air pipe in a direction in which the air is to be moved, wherein the airflow generating unit comprises a fan, wherein the airflow generating unit operates so that an airflow rate on a side of the air-permeable member into which the air flows is 0.2 m³/min or higher.
 20. An image forming apparatus comprising: an air discharging unit that sucks air that is present in an apparatus body and discharges the air, wherein the air discharging unit comprises a duct, wherein the particle collecting device according to claim 1 is disposed in combination with the air discharging unit.
 21. A particle collecting device comprising: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller, wherein a thickness of a boundary portion between the cells of the honeycomb structure is 0.015 mm or larger and 0.02 mm or smaller.
 22. A particle collecting device comprising: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller, wherein the air-permeable member is made of aluminum.
 23. A particle collecting device comprising: an air pipe having a flow space in which air including particles flows; a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller; and an airflow generating unit that generates airflow that causes the air to flow in the flow space of the air pipe in a direction in which the air is to be moved, wherein the airflow generating unit comprises a fan, wherein the airflow generating unit operates so that an airflow rate on a side of the air-permeable member into which the air flows is 0.2 m³/min or higher.
 24. An image forming apparatus comprising: an air discharging unit that sucks air that is present in an apparatus body and discharges the air, wherein the air discharging unit comprises a duct; and a particle collecting device, the particle collecting device comprising: an air pipe having a flow space in which air including particles flows; and a collecting unit that is disposed in such a way as to block the flow space of the air pipe and that collects the particles included in the air, wherein the collecting unit is a plate-shaped air-permeable member having a honeycomb structure such that a number of cells per square inch is 600 or larger and 1400 or smaller, wherein the particle collecting device is disposed in combination with the air discharging unit. 